Issues with Lambda Sensor Reading...
Hi Guys,
Some of you may know, I have a 170bhp G40 in my Mk2 Polo.
I have a narrowband lambda sensor connected to the purple (or lilac as the haynes states) wire coming from the loom end of my lambda sensor.
It used to bounce back and forth between lean and rich, as you would expect, and sit at the rich end when on boost, and when on overrun (foot off throttle, decellerating) it would go towards the lean end of the scale.
On our trip to Europe, the car stop registering the rich end of the scale, and stopped scrolling, the entire lean->stoich range of LEDS was lit up, upon boost the leds for stoich only would light up.
I have since fitted another lambda that was sitting in the unit (unknown if its working correctly) but now the guage reads lean all the time, most times not even registering on the guage! This is just under normal operating conditions, I have not been driving the car on boost since.
I did accidently ground the sensor wire from the guage to the earthing point on the inlet manifold, but it was not connected to the lambda sensor at this point.
Could I have either damaged the AFR guage by grounding the signal wire, or could both lambda guages be duff? I have two other ones I can try, one from my Mk3 G40 which is running sweet and one from the turbo Mk2 which I havent run yet.
I have checked for boost leaks, of which I have none. The boost guage before would only read 5-8psi max, but now that I have modified my alternator bracket, I can get more tension on the belts which has given me a considerably higher boost reading.
Yesterday I fitted a new fuel pump (in-line), as well as a rebuilt charger. The car runs very well, except on full boost, I have been having some slight juddering - I replaced all the ignition components (Coil, Rotor Arm, Dizzy Cap, Spark Leads) in a bid to cure this to no avail. I have a replacement distributor I can try, and I need to whip out the spark leads this evening to check the condition of them.
During the Europe trip when the guage stopped scrolling, I have checked the spark leads every 500 miles and they were always a nice grey colour. Will check this evening before I set off and see what they are like.
Any ideas? I'm going to try another lambda sensor tonight, along with another AFR guage. although I really could do with buying a wideland lambda, or getting it on a gas analyser.
I also have a brand new in-tank pump I can replace
One thing I've never done, nor checked, is the CO pot value.
Ta :)
Hey Saf
The signal that the 'gauge' gets from the narrowband lambda will vary 0.2-0.8v depending it it's lean 0.2v or rich ~0.8v.
I'm a bit confused though, when you say "I have since fitted another lambda that was sitting in the unit (unknown if its working correctly" and "or could both lambda guages be duff?" - have you changed the sensor, the gauge or both?
I'd start by assuming the connection to the sensor itself, or the lambda sensor is at fault. You can check with a multimeter to the purple signal wire and the sensor's ground - check when warm that the value varies 0.2-0.8v. NEVER check the sensor resistance, as you'll kill it.
Really though, stop wasting your time and buy a wideband! One of the best things I ever bought for the car.
Hey dude, swapped out the original lambda probe with another probe I found in the unit yesterday. I say swapped, I fitted it to the 2nd exhaust lambda boss, which had a blanking plug in as I couldnt get the original lambda probe out (siezed to fook)
Fitted another afr gauge (still a narrowband) today before I came home from work and still just sits at the leaner end of the stoich portion of the guage. Exactly the same as the one that was fitted previously.
Any recommendations on wideband to get?
I'm guessing ill need a new standard probe as ive read you cant use the wideband probe to provide a signal to the ecu
Cheers for the reply man ill get a wideband on order asap
Hmmm... it's quite bizzarre the symptoms you're having.
Wideband, I have an AEM Uego which is ok but smooths the display a bit too much for my liking. i.e if you go from 11:1 to 15:1 it'll take 3-5secsonds or so to show 15:1 as it scrolls through 11.1:1, 11.5:1, 12.2:11 etc. I'd prefer if it just said 11:1 then straight to 15:1, although it could be a bit distracting as it changes around. Stack are supposed to be ok too but if you can afford it I'd go for the Zeitronix that Yoof runs - looks like a sweet bit of kit.
Are innovate lm1 and 2s no.goes? Do you need to run both probes, one for the.ecu, one wideband? Or can the wideband provide an ecu signal?
Those zeitronix do look like.neat pieces of kit. I can probaby just stretch to one. The additional plug in modules seem like it would be a worthwhile investment anyhow
Hah. Went to fit a new one today, unplugged it by the loom end and.noticed 2 pins missing! Checked underneath and it had got caught in the drivshaft and ripped the wiring apart! New lammy fitted and all is reading as it should be :-) so I can go back to running in the charger now with peace of mind :-)
The original lambda which is still seized in, was def pooped tho!
Ta for the input Chris!
No worries dude, glad you've got it fixed.
Still need a wideband thought ;)
Yeah cheers man dont worry im on it, on the lookout for a decent one with datalogging as itll be helpful for all my cars including the carbd valvers!
If your ever up in manc and have some free time pop over for a cuppa :-)